Refusing to allow people to be paid less than a living wage preserves to us our own market. There is absolutely no use in producing anything if you gradually reduce the number of people able to buy even the cheapest products. The only way to preserve our markets is to pay an adequate wage. -- Eleanor Roosevelt

I've always used bars. If you didn't smelt it down you'd be ripping off ray for the total of 5/8 a piece of coal every time your portal moved. Also, the automated system for buying other items probably only accepts bars.